Analysis of Buffer Delay in Web-Server Control

Summary, in English

This paper addresses a problem related to control of web servers. Due to architectual issues, relevant measurements can only be taken over a limited part of the server system, which leaves the controller unaware of what happens in buffers proceeding the actual web-server (for instance, in the TCP/IP layers). In earlier presented work we modeled such a system and proved that the unmeasured buffering turned a measurement of an input disturbance into a state-dependent variable. In this paper we investigate how these new properties effect a traditional control design consisting of feedback in combination with a feed-forward mechanism. The stability analysis suggests that under certain circumstances, the system enters limit cycles due to the feedback mechanism introduced by the designed feed-forward controller. We verify the analysis by both simulations and experiments.

• Författare: Martin Ansbjerg Kjaer; Anders Robertsson
• Avdelning/ar: Institutionen för reglerteknik; ELLIIT: the Linköping-Lund initiative on IT and mobile communication
• Publiceringsår: 2010
• Språk: Engelska
• Sidor: 1047-1052
• Publikation/Tidskrift/Serie: 2010 American Control Conference
• Dokumenttyp: Konferensbidrag
• Förlag: IEEE - Institute of Electrical and Electronics Engineers Inc.
• Ämne: Control Engineering
• Conference name: American Control Conference, 2010
• Conference date: 2010-06-30 - 2010-07-02
• Conference place: Baltimore, MD, United States
• Status: Published
• Forskningsgrupp: LCCC
• ISBN/ISSN/Övrigt: ISSN: 0743-1619